The present invention is directed to environmental control systems, and more particularly, to a purge ejector for a pressure swing adsorption (PSA) NBC filtration system which communicates with high-pressure drain ducts.
Modem vehicles generate a large quantity of thermal energy that must be effectively dissipated, i.e., by cooling, to ensure continuous, reliable operation of the avionics/electronic modules. To dissipate such thermal energy, vehicles typically include an environmental control system (ECS) that provides a temperature/pressure regulated airflow for cooling of the avionics/electronic modules. The regulated airflow is generally further utilized for crew comfort, and may be used for over pressurization to preclude contaminant infiltration.
Military vehicles in particular maybe exposed to chemical, biological, and/or nuclear hazards. As a result, such vehicles are typically equipped with a nuclear/biological/chemical life support system (NBC LSS) to facilitate operations under such hazardous conditions. The NBC LSS ensures that NBC particulates/contaminants are removed from the airflow processed by the ECS. Integrated environmental control systems typically combine the ECS and the NBC LSS functions into a single integrated environmental control system that provides a decontaminated, cooled airflow for cooling of avionics/electronic modules and crew comfort.
It is known to utilize a pressure swing adsorption (PSA) NBC filtration system as part of an integrated environmental control system. PSA performance is affected by the difference in adsorb and desorb pressures and the quantity of airflow used to purge contaminants. The greater the difference (pressure swing), or the higher the purge flow, the better the PSA performance. The desorb process is endothermic and as the pressure swing or purge flow is increased there maybe an increased likelihood of a purge exhaust duct freezing in a low temperature environment. Thus, to increase the pressure swing or purge flow while minimizing the likelihood of freezing, a larger ducting system must be supplied which results in an undesirable weight increase.
A need therefore exists to provide an integrated environmental control system that has increased operating efficiency, a lower overall system weight, and a minimized risk of freezing in low temperature environments.
The integrated environmental control (IEC) system according to the present invention includes a decontamination Pressure Swing Adsorption (PSA) system in which a contaminated decontamination bed is purged through a purge exhaust duct. The contaminated airflow passes through the purge exhaust duct and is subsequently dumped overboard through a purge ejector. A high pressure drain duct such as a water separator drain duct and/or a High Efficiency Particulate Air (HEPA) filter drain duct communicate with the purge ejector.
The energy from the water separator drain duct and the filter drain duct serve as the primary motive force for the purge ejector to create a sub-atmospheric region therein and reduce back pressure upon the PSA filtration system. The reduced back pressure essentially creates additional pressure drop across the PSA filtration system which improves PSA filtration system performance. This, in turn, means that smaller components maybe used for system flow ducting or greater purge flow for the same passageways. A significant reduction in overall weight of the IEC system is thereby provided.
The water separator drain duct and the filter drain duct are not subjected to the endothermic desorption process of the PSA filtration system prior to being mixed in the purge ejector with the relatively colder contaminated airflow exhausted from the PSA system. Risk of the purge exhaust duct and the purge ejector freezing in a low temperature environment is thereby minimized.
In another embodiment of the instant invention, the purge ejector communicates with a ram air duct to further intensify the sub-atmospheric region and the pressure swing.